Radiation pressure effects at the focus of intense lasers

State-of-the-art lasers can now reach intensities well in excess of 1020 Wcm-2 at focus. When directed onto a target that is sufficiently dense that it can stop the laser beam, the intense radiation pressure can directly drive the critical density surface of the target. This can manifest itself in a number of ways. It can drive a collisionless shocks which can be diagnosed by the ions it accelerates in its path. Alternatively, for sufficiently thin targets, the whole plasma can be propelled forward gaining momentum as it propagates. The result in both cases is the production of dense beams of energetic ions. These ions could have numerous applications, not least in next-generation particle accelerators. The project proposed here will investigate radiation pressure driven acceleration schemes through optimisation of targets and of the characteristics of the laser beam that drives them. The experiments will take place on the high intensity lasers at the Rutherford-Appleton Laboratory and the IR laser at the ATF Brookhaven National Laboratory. A near term goal is to produce protons with energies exceeding 100 MeV, which would be of interest for applications such as radiation treatment of tumours or for fast heating of fusion capsules.